Refining of styrene crudes



Patented Dec. 7, 1943- 9 UNITED ST T S PATENT' OFFICE 2.336.259 nnr mmo or" smear: canons Wilbert A. King, Mem

Atlantic City,

Kieiner,

piris, Tenn.,

Iulins H.

N. .L, and Allen B.

' Krotzer, Philadelphia, Pa., assignors, by mcsne assignments, to Allied Chemical & Dye Corporation, a corporation or New York Application Deeember 30,1940, Serial No. 372.360

No Drawing.

9 carat, (cl. zoo-cs9).

This invention relates to the removal orinactivation of constituents which deleteriously or adversely afiect heat polymerizationin oils used in the production of polystyrene resins.

, Crude styrene fractions produced by fractional distillation of the crude oils which generally serve as a source of styrene for the production of polystyrene resins contain materials which deleteriously or adversely afiect heat polymerization of the styrene. The effect of these inhibitors or retarding,agents is twofold; they reduce the rate of heat polymerization and impair the ultimate polymer. The reduced rate or polymerization is a disadvantage ;since it raises production costs. The impairment of the polystyrene is reflected in reduced average molecular size of polymer and possibl in altered molecular arrangement. Not only do the deleterious constituents reduce the average molecular weight of polystyrene but also they may influence the range and distribution of the variously sized'molecules which are comprehendedin the average molecular weight. There is reason to believe that under varying polymerization conditions the moleculararrangement of polystyrene may be altered, i. e. in place of long-chain polymers, corresponding molecular weight polymers in the form of bundles" of short chains held together possibly by secondary valences may prevail.

The reduction in the average size o! the p ymer molecule is a serious disadvantage since high molecular complexity, i. e. large polymer size. is one of the more important specifications for commercial polystyrene. The melting point of the polystyrene resin, for example, and the toughness of the'resinin a solid state are dependent upon molecular complexity. A resin of high molecular complexity usually produces high-viscosity solutions whichare valuable in industry.

The other factors, the range and distribution of Y molecular sizes making up the averagemolecular weight of the polystyrene, and the type of molecular structure, may also influence the physical properties of the styrene resin to diflerent expolymerization of the styrene are substantially completely inactivated or eliminated without substantlal polymerization or other deleterious eilect on the styrene.

As disclosed in the said pending application 1 Serial No. 349,279, the sulfuric acid treatment eflects the inactivation or removal of certain inhibitors which tend to aflect deleteriously the polymerization of styrene during subsequent heat polymerization. While the exact chemical composition ot the materials removed by the subsequent treatment with the mercury compound is not known, we believe that this treatment effects hydration of the acetylenic constituents, particularly phenyl acetylene, which are not removed by the sulfuric acid treatment and which, if present. would tend to inhibit polymerization of the styrene and thereby affect the quality or the styrene polymer produced upon subsequent heat polymerization. The hydrated acetylenic constituents may be readily removed by distillation before polymerization is carried out.

' Styrene oils which may be treated by the prqc-. ess of our invention, and which are intended to be included within the term styrene oil as used in the claims, include the various crude resin oils generally used as a source of styrene for the production oi! polystyrene resins. Styrene or a homolog of styrene is the principal polymerizable constituent in such oils. A examples oi styrene oils there may be mentioned the styrene fractions of drip oil (the oil whichsettles out of gas mains), coke oven oil and tar distillates,

' cracked petroleum, the crude product of styrene synthesia'and the styrene fraction from the prodtents. Thus, for example, it has not-infrequently been found that two polystyrene resins with the same melting point will yield in solution markedly different viscosities. a

Itis an object of thisinvention to provide a novel process for treating styrene crudes to efiect the removal of constituents which deleteriously or adversely affect heat polymerization, so that upon subsequent polymerization there results a high yield of polystyrene having advantageous not of pyrolysis oi polystyrene. Resin crudes useful for polystyrene resin production generally contain about 20% or more by volume of styrene, which term is used herein to include. homologs thereof, although in some instances a crude con-'- taining as low as 10% or less styrene may be employed for resin production.

' The process of this invention is of particular importance for removing or inactivating polymerization inhibitors or retarding agents from styrene oils rich in styrene. For example, "closeapplication Serial No. 349,279, filed fractions of a boiling cu styrene fractions of drip oil, i; e. styrene be treated by our process- (Sulfuric acid pretreatment of the styrene oil is carried .out under conditions so as to avoid the deleterious effect on the styrene and the sub stantial polymerization of styrene. To accomplish this, the process variables such as strength of acid, amount of acid, time of treatment and temperature of treatment are carefully controlled; that is, when strong sulfuric acid is employed (55 B.) the amountbfacid, or the time and temperature of treatment are so regulated and correlated that the styrene is not adversely affected." Generally the strength of acid is restricted to about 55 of 40 .to 55 B., preferably 50 .B., is preferred. S Y

The amount of acid used isvaried with relation I to the other variables in the process, i. e. the concentratlon of acid, time andftemperature of treatment. Generally. 5% or less acid based on the weight of the crude will be found satisfactory. The use of about 3% the crude is preferred.

When treatinga'styrene oil conta ning a sub- I 'stantial amount of inhibitor material, it is ad vantageous to subject the oil to two or more successive washings with sulfuric acid, preferably using not more than about 5% acid. based on the weight of the oil, in each washing operation. To determine the number of washing ooerationsrquired by any particular oil to removal or inactivation of hibitors, the oil may be tested at the end of each successive sulfuric acid wash by carrying out an experimental polymerization todetermine whether the desired results in' yield (and'polymer size have been obtained. Generally, it is advantageous to agitate the oil with sulfuric acid for about an hour in each of the washing operations, although depending upon the strength or concentration of the acid and the degree of agitation employed. Crude styrene containing oils which have not been polymerization insubjected to fractionation to separate a fraction richin styrene generally require longertre'atment, or treatment with stronger acid, than the close-cutstyrenefractions.

B. or less. An acid strength pera'ture up to about 70 a greater amount of acid may be used.

In a preferred method of carrying out our invention, the styrene fraction is agitated for about one hourwith 3% acid. This treatment may be repeated three or four times as'above indicated, the sludge being removed between each treatment: After remov-.

ing the sludge from the final treatment, the

crude is ready for the mercury compound treatment described below. x 1

Following the sulfuric acid treatment hereinlarly phen-yl acetylene.

mercury may be dissolved in sulfuric-or other acid ,eto from a solution of a mercuric or mercurous acid based on the weight of I obtain satisfactory a longer or shorter time may be used.

The temperature during the sulfuric acid treatment is generally limited to below about 70 C. and preferably below about (3.,for an acid of 50 B. or higher concentration. When. several successive Washing operations are employed it is advantageous to carry out the first washings at lower temperatures, for example, about room temperature. In general, the temperature should also be so correlated with the time of contact, strength and quantity of acid as to prevent any considerable loss of styrene by catalytic or heat polymerization,= or by other reaction; for example, a

when operating with an acid of about 50 B.

the temperature should generally not exceed 50 C. and the amount used is preferably about 2% to 3% based on the weight of the crude treated.

Usinga-weaker acid, say about 50 B., a temcrude. Solutions of compound, and the resulting solution to about 75% reaction makes the process commercially practicable. g In a preferred method of carrying out the treatment, from about 4% to'1% chemically equivalent amount of other mercuric compound, based onthe-weight of the crude, is dissolved in 20% sulfuric acid and this solution is considered complete, On completion of the re- .pz ocess ofour invention:

A styrene fraction obtained by fractionating a light oil 'of gas plant origin and collecting a out having a distillation range of from 142 to 146 (3., the fraction containing approximately styrene, the remainder being chiefly orthoxylene, was divided into two portions. One por- C. may be, employed, and

by weight of 50 B. sulfuric relatively small pro- I mercuric sulfate or redistilling, agitating the distillate vigorously with an excess nitrate; if noprecipitate is .tion of this fraction was 300 grams, and part 3, .324 grams. three parts were added respectively 3.6, 1.73 and respectively 1,11,058 and-0.28.,

Q to be free thereof.

' of acid after which when the distillate failed to acetylide precipitate during agitation with amassent!) agitated for one-hour with by volume of 50 Be. sulfuric acid, the acid sludge then settled and withdrawn. This acid treatment was twice repeated,- using fresh 50 B. acid each time- Duringthe first two acid treatments the temperature was within the range 28 to 30 C., and during the third treatment the temperature was raised to 50 C. The recovered oil layer was divided into three parts, part 1 containing 324 grams, part 2 containing To these 0.91 grams of mercuric sulfate in 100 ml. of sulfuric acid; the percentage by weight of mercuric sulfate based onthe, weight of the oil was The resultant mixtures were'agitated until upon.testing for acetylenic constituents the mixtures were found The time of agitation for each part was 3, 4 and 6 /2 hours respectively.

The tests for acetylenic constituents hereinabove mentioned were made on each agitator every half hour as follows: The agitation was ,stopped and, after allowing five minutes for settling, a small sample of the oil was withdrawn ,bypipett'e. This sample was washed with strong neutralize traces the separated oil was diswas pronounced complete sodium hydroxide solution to tilled. The reaction rnoniacal silver nitrate.

When each of the above to be free of acetylenic constituents, i. e. upon completion of the agitation, parts 1 and'2 were combined and the acid. layer withdrawn. The

bil layer was filtered, neutralized with sodium hydroxide, and distilled. added to the distillate containing 60% styrene, heated at 100 C. to producepolystyrene. .The polymer recovered from its solvent had a viscosity at C. of 4125 centipoises when dissolved in toluene to form a Ortho-xylene was to produce a mixture and this mixture' was 25% by weight solution. y

We have found it is important to carry out the constituents by treatdescribed and subsequent to removal of the acetylenic ment as herein treatment of crude with sulfuric acid; by so doing, more complete removal or inactivation of inhibitors which affect the polymerization of styrene may be accomplished in less time or with less mercuryreagent than would be possible without prior sulfuric acid treatment. This is illustrated by the following:

A second portion of the crude without treatment with sulfuric acid as hereinabove described was divided into three parts, constituted of 301, 346 and 304 grams respectively, these three parts treated with 3.34, 1.9'! and 0.82 grams of mercuric sulfate dissolved in 100ml. of 20% the percentage by weight of mercuric sulfate relative to amount of oil treated being 1.11, 05'7 and 0.27 respectively. The mixtures were agi v tated and periodically'tested as hereinabove described to determine whether or not acetylenic constituents had parts 1 an d'2 they were found to be free of acetylenic compounds after agitation for 5 and 6 hours respectively. In the case of part 3, acetylenic material was still present after 14 hours, at which time the experiment was discontinued. Parts 1" and 2 were combined when free of acetylenic constituents, the acid layer withdrawn, and the oil layer filtered. This oil layer form the metal three parts was found for 120 hours in a sealed flask sulfuric acid,

been removed. In the case of was then subjected to three washings with B. sulfuric acid, exactly as described in connection with the operations involving the acid treat ment prior to the mercuric sulfate treatment.

The acid-treated materialwas neutralized and distilled. The distillate was adjusted to styrene concentration with the addition of orthoxylene and polymerizedat C. for hours in a sealed flask in exactly the same manner as the polymerization tions, hereinabove described. The viscosity, at 25 C. of the 25% polymer solution in toluene was found to be 34'70 centipoises; this compares with a viscosi ty of 4125 centipoises in the case was of the polymer produced by polymerization of .freed of inhibitors,-as shown by the increased viscosity of the polymer. Moreover; for a given treatment time appreciably less mercury reagent will be needed if the sulfuric acid pretreatment is used. -It further appears that treatment of the crude with sulfuric acid prior to treatment with the mercuric sulfate or other mercury compound ciits down the side reactions during the mercury-compound treatment and thus results in a substantial economy in the mercury reagent.

employed to effect inactivation or removal of acetylenic-type polymerization inhibitors.

iii

In operation it has been ment of styrene crudes with sulfuric acid followed by mercuric sulfate orother mercury compound treatment as hereinabove comparatively simple to carry out ahd results in substantially complete removal or inactivation. of

inhibitors which tend to inhibit or detrimentally affect the polymerization of styrene.

Removal of acetylenic bodies by the mercury compound treatment of this invention is positive and highly effective in that an irreversible "hydration of the acetylenic bodies takes place when the crude is treated with the mercury reagent. When other reagents, e. g. cuprous salts, which have been tried, are used, instead of hydration of acetylenic bodies acetylides are formed by addition. This addition reaction ,appears to be reversible so that the metal acetylides tend to decompose and liberate the acetylenic bodies. Furthermore, cuprous reagents are difficult to handle since they are readily changed to the eupric state in which form they are unreactive.

The term polymerization inhibitor has been used broadly in the specification and claims to cover the constituents which deleteriously or adversely affect heat polymerization of styrene.

The mechanics of the inhibition are not clearly understood and this application is, therefore, not limited to any particular type of deleterious constituents in the styrene oil. I

The term inactivate" has been used in various forms in the claims in a broad sense to include either removal or inactivation of the deleterious constituents of the styrene oil.

Since certain changes may he made in carrying out the above process without departing from the scope of the invention, it is intended that all matter container in the above description shall be interpreted as illustrative and not in a limitconducted in the operafound that the treat described is We claim: v improvement which comprises inactivating sty- 1. A process for inactivating styrene polymerrene polymerization inhibitors in the oil by treatcQmprises treating the oil with sulfuric acid of 5 based on the weight of the crude, at a tempera- I not morethan 55 B. concentration and at a ture not higher than 50 C., and thereafter agitemperature nothigher thani70 C. for acid of tating the partially purified oil with a sulfuric less than 50 B. concentration and not higher acid solution containing A to 1% by weight of than 50 C. for acid of a concentration of 50 B. mercuric sulfate based on the weight of the oil,

to 55 B. and thereafter treating the oil with a neutrallzing the acid and distilling the neutralreagent comprising a mercury salt'tc effect a subized oil to separate, as distillate, oil substantially stantially complete inactivation of polymerizaree of acetylenic constituents. tion inhibitors without substantial adverse ef- P s for n c ivat ng styrene po l'- 2. A process for inactivating styrene polymerl5 co itaini g' inhibitors of the acetylen c yp taining inhibitors of the acetylenic typewhich acid a concentration of more than comprises treating the oil with sulfuric acid of in amount not e then 5% based on the a concentration of t more than 55 e t; weight of the crude, at a temperature not higher temperature not higher than 70 0., and therethan after agitating the oil with a reagent comprising the oil, agitating the thus partially purified oil a mercury salt; with a mercuric salt and distilling the thus 3. A process for inactivating styrene polymertreated" oil to separate, as distillate, oil substanzation inhibitors in an impure. styrene oil conl y free of ac t ni c n i ent etylenic. type which 2 8. In a process for inactivating polymerization comprises treating the oil with sulfuric acid of inhibitors in a Crude Styrene on f drill);

a concentration of not more than 55 B. at a oil, the improvement which comprises treating temperature not higher than 70 0,; thereafter said fraction successively with portions of sulagitating the oilwith a reagent comprising a furic acid of concentration of about 50 B., the mercury salt dissolved in an acid solution, new amount o'feach portion being not more than tralizing the resultant acidified oil mixture, filter- 5% based on the weight of the crude, at a teming the neutralized oil mixture and distilling the perature not higher than 70 C., removing the filtrate to separate;- as distillate, the purified styspent acid sludge aft r a h men and rene o 4. A process f inactivating styrenepolymerlast treatment with a sulfuric acid solution conization inhibitors in an impure styrene oil containing /4 to 1% by Weight 0 mercuric sulfate a concentration of not mor than 55 B. at a rate, as distillate, oil substantially free of acetytemperature not higher than 70 0.; thereafter lenic constituents process for inactivating styrene polymer- I as distill te, th purified styrene 1 concentration about B., the amount of each f a concentration of about 40 to B., in 50 ered from the last treatment with a sulfuric acid amount not morethan 5% based on the weight ution conta ing A to by Weight of mer-v of the crude, t; a temperature of t; highe curic'sulfate based on the weight of the oil, filthan 0., and thereafter treating the crude terlng' the resultant mixture, neutralizing the with a sulfuric acid solution or a mercuric salt filtrate and distilling the neutralized filtrate to in amount from A to 5% of mercuric salt based 55 separate, as distillate, oil substantially free of on the weight of the crude oil. treated. i t e c con t uen s.

6. In a process for inactivating styrene polyv WILBERT A. KING.

merization inhibitorsin an impure styrene oil J L US NER- containing inhibitors ofthe acetylenic type, the l ALLEN R. KROTZER. 

